The process of this invention relates to the production of 17.alpha.-acetoxy-1,2-methylene-4,6-pregnadiene-3,20-dione which can be used conventionally in the synthesis of the known steroid hormone cyproterone acetate (6-chloro-17.alpha.-acetoxy-1,2-methylene-4,6-pregnadiene-3,20-dione).
According to the known synthesis, .sub..DELTA. 1,6-hydroxyprogestrone is reacted with dimethylsulfoxonium methylide to form the 1.alpha.,2.alpha.-methylene compound (DE PS 1,183,500). However, this process has the drawback that this methylenation reaction does not progress uniformly, since the methylenation reagent also partly attacks the 20-keto group.